The goals of this research project are to identify genes required for mammalian development and to investigate the functional content of the chromosomal region defined by the piebald deletion complex. As genomic sequence information is compiled, the structural and regulatory organization of the genes identified will need to be linked with biological function. Mutagenesis screens, relying on phenotype-driven detection of genetic variation, provide an opportunity to establish this connection. In this proposal we will combine genetic studies with computational and comparative genomic sequence analysis to functionally annotate a defined genomic region. The piebald deletion complex is a collection of overlapping deficiencies that encompass a 15-18.5 cM/-39 Mb interval of distal mouse chromosome 14. Several loci important for development have been mapped within this region, resulting in the characterization of mouse models for understanding gastrulation, skeletal patterning and crarnofacial defects, spinal cord malformation and respiratory distress at birth. Computational and comparative genomic analysis to identify genes and additional conserved sequence features will be merged with functional studies. A traditional two-generation regionally directed ENU mutagenesis screen that takes advantage of the piebald deletions and coat color spotting will be used to recover recessive mutations that are essential for development. In addition, we will develop and employ a novel EGFP-based reporter system that takes advantage of the enhanced green fluorescence protein (EGFP) and color variants to conduct a one generation genetic screen that incorporates the recently developed protocols for embryonic stem cell mutagenesis. This approach offers a higher mutation frequency, the use of a wider variety mutagens, and instant visual classification of all screen-derived progeny (mice and embryos) facilitating in depth phenotype analysis. The mutations recovered in the screen will be fine mapped using the deletion panel in order to identify the gene associated with the mutant phenotype. Together, these approaches will enrich the mouse mutant resource and provide new insights relating biological function with chromosome content and organization.